Technical Field
This application relates to a vascular surgical apparatus, and more particularly to a minimally invasive device for removing plaque or other deposits from the interior of a vessel.
Background of Related Art
The vascular disease of atherosclerosis is the buildup of plaque or substances inside the vessel wall which reduces the size of the passageway through the vessel, thereby restricting blood flow. Such constriction or narrowing of the passage in the vessel is referred to as stenosis. In the case of peripheral vascular disease, which is atherosclerosis of the vascular extremities, if the vessel constriction is left untreated, the resulting insufficient blood flow can cause claudication and possibly require amputation of the patient's limb. In the case of coronary artery disease, if left untreated, the blood flow through the coronary artery to the myocardium will become inadequate causing myocardial infarction and possibly leading to stroke and even death.
There are currently several different treatments for treating arterial disease. The most invasive treatment is major surgery. With peripheral vascular diseases, such as occlusion of the tibial artery, major surgery involves implantation and attachment of a bypass graft to the artery so the blood flow will bypass the occlusion. The surgery involves a large incision, e.g., a 10 inch incision in the leg, is expensive and time consuming for the surgeon, increases patient pain and discomfort, results in a long patient recovery time, and has the increased risk of infection with the synthetic graft.
Major surgery for treating coronary artery disease is even more complex. In this surgery, commonly referred to as open heart surgery, a bypass graft connects the heart to the vessel downstream of the occlusion, thereby bypassing the blockage. Bypass surgery requires opening the patient's chest, is complex, has inherent risks to the patient, is expensive and requires lengthy patient recovery time. Bypass surgery also requires use of a heart lung machine to pump the blood as the heart is stopped, which has its own risks and disadvantages. Oftentimes, the saphenous vein in the patient's leg must be utilized as a bypass graft, requiring the additional invasive leg incision which further complicates the procedure, increases surgery time, lengthens the patient's recovery time, can be painful to the patient, and increases the risk of infection.
Attempts to minimize the invasiveness of coronary bypass surgery are currently being utilized in certain instances. These typically include creating a “window approach” to the heart. Although the window approach may reduce patient trauma and recovery time relative to open heart surgery, it still requires major surgery, and is a complicated and difficult surgery to perform due to limited access and limited instrumentation for successfully performing the operation. Attempts to avoid the use of a heart lung machine by using heart stabilization methods has become more accepted, but again, this does not avoid major surgery.
Due to the invasiveness and potential for complications with major peripheral or coronary vascular surgery, minimally invasive procedures have been developed. Balloon angioplasty is one of the minimally invasive methods for treating vessel occlusion and obstructions. A catheter having a balloon is inserted through the access artery, e.g., the femoral artery in the patient's leg or the radial artery in the arm, and advanced through the vascular system to the occluded site over a guidewire. The deflated balloon is placed at the occlusion and inflated to crack and stretch the plaque and other deposits to expand the opening in the vessel. Balloon angioplasty, especially in coronary surgery, is frequently immediately followed by insertion of a stent, a small metallic expandable device which is placed inside the vessel wall to retain the opening which was created by the balloon. Balloon angioplasty has several drawbacks including difficulty in forcing the balloon through the partially occluded passageway if there is hard occlusion, the risk involved in cutting off blood flow when the balloon is fully inflated, the frequency of restenosis after a short period of time since the plaque is essentially stretched or cracked and not removed from the vessel wall or because of the development of intimal hyperplasia and the possibility of balloon rupture when used in calcified lesions.
Another minimally invasive technique used to treat arteriosclerosis is referred to as atherectomy and involves removal of the plaque by a cutting or abrading instrument. This technique provides a minimally invasive alternative to the bypass surgery techniques described above and can provide an advantage over balloon angioplasty methods in certain instances. Atherectomy procedures typically involve inserting a cutting or ablating device through the access artery, e.g., the femoral artery or the radial artery, and advancing it over a guidewire through the vascular system to the occluded region, and rotating the device at high speed to cut through or ablate the plaque. The removed plaque or material can then be suctioned out of the vessel or be of such fine diameter that it is cleared by the reticuloendothelial system. Removal of the plaque in an atherectomy procedure has an advantage over balloon angioplasty plaque displacement since it debulks the material.
Examples of atherectomy devices in the prior art include U.S. Pat. Nos. 4,990,134, 5,681,336, 5,938,670, and 6,015,420. These devices have elliptical shaped tips which are rotated at high speeds to cut away the plaque and other deposits on the interior vessel wall. A well-known device is marketed by Boston Scientific Corp. and referred to as the Rotablator. As can be appreciated, in these devices, the region of plaque removal is dictated by the outer diameter of the cutting tip (burr) since only portions of the plaque contacted by the rotating tip are removed. The greater the area of plaque removed, the larger the passageway created through the vessel and the better the resulting blood flow.
U.S. Pat. Nos. 5,217,474 and 6,096,054 disclose expandable cutting tips. These tips however are quite complex and require additional expansion and contraction steps by the surgeon.
U.S. Pat. No. 6,676,698 discloses an atherectomy device designed to obtain an optimal balance between the competing objectives of the smallest introducer sheath size to facilitate insertion and reduce trauma to the vessel and the largest atherectomy tip size to remove a larger region of plaque or other deposits from the vessel wall.
However, it would be advantageous to enhance the breaking up and removal of the small particles in atherectomy procedures.